Plant oils such as triacylglycerols (TAGs) are useful for food, industrial feedstock and biofuel production. TAG is generally harvested from the seeds of oil crop species, such as canola. However, engineering of crops that product oils in non-seed tissues (leaves and roots) is an alternative way to produce feed stocks for high energy transportation biofuels or even jet fuels.
Fuels are typically produced from petroleum products, but such production involves considerable cost, both financially and environmentally. Sources of petroleum must be discovered, but petroleum exploration is an expensive and risky venture. The cost of exploring deep water wells can exceed $100 million. In addition to the economic cost, petroleum exploration carries a high environmental cost. For example, offshore exploration frequently disturbs the surrounding marine environments.
After a productive well is discovered, the petroleum must be extracted from the Earth, but such extraction is expensive and, even under the best circumstances, only 50% of the petroleum in a well can be extracted. Petroleum extraction also carries an environmental cost. For example, petroleum extraction can result in large seepages of petroleum rising to the surface. Offshore drilling involves dredging the seabed which disrupts or destroys the surrounding marine environment.
After extraction, petroleum must be transported over great distances from petroleum producing regions to petroleum consuming regions. In addition to the shipping costs, there is also the environmental risk of oil spills.
In its natural form, crude petroleum extracted from the Earth has few commercial uses. It is a mixture of hydrocarbons (e.g., paraffins (or alkanes), olefins (or alkenes), alkynes, napthenes (or cycloalkanes), aliphatic compounds, aromatic compounds, etc.) of varying length and complexity. In addition, crude petroleum contains other organic compounds (e.g., organic compounds containing nitrogen, oxygen, sulfur, etc.) and impurities (e.g., sulfur, salt, acid, metals, etc.). Hence, crude petroleum must be refined and purified before it can be used commercially.
Due to the inherent challenges posed by petroleum, there is a need for a renewable petroleum source which does not need to be located by extensive exploration, extracted, transported over long distances, or substantially refined like petroleum. There is also a need for a renewable oil source that can be produced economically without environmental damage.